1. Field of the Invention
This invention relates to a method for partially plating on a base of synthetic resins or other materials including not only a single base but an assembly thereof comprising a number of chip bases, and more particularly relates to a method for partially plating on bases to be used for producing electronic and electric parts such as printed circuit board, lead frame insert molded circuit parts, etc.
2. Description of the Related Art
There has been known how to partially plate on a synthetic resin base or molded article as in the following;
(1) according to a conventional method, the surface of a molded article is roughed, for example, by etching, followed by addition of a Pd- or Pt-catalyst and application of resist thereon, except a portion to be plated, by a silk screening or dispenser coating, and is then subjected to a plating process, the resist being finally removed therefrom, and
(2) according to the other conventional method, a molded article which has been roughed and catalyzed as described above is inserted in a mold, coated with an insulating material such as plastics or gum by injecting the material into the mold while leaving a portion to be plated in an uncoated condition and is then subjected to a plating process, the thus coated material being removed, if necessary. (See, xe2x80x9cPlastics Seikeikakou no Fukugouka Gijutsuxe2x80x9d (Combined Technology of Plastics Molding), CMC Co., Ltd., pp. 260-275; JP-A No. 7-316825; JP-A No. 63-4,092 and Registered JP No. 2,592,243).
In the above mentioned method (1), however, it is necessary to conduct a resist hardening process by heat-drying, etc. after the resist is applied. Further, an organic solvent such as methylene chloride should be used to remove the resist after the plating process. Such an organic solvent is considered as an origin substance, like chlorofluorocarbon (CFC), which causes the failure of ozone layer and would bring about an increase in skin tumor and cataract or undesirable change in ecosystem of plants, plankton, etc. when a large quantity of solvent is wasted.
In the other method (2), on the other hand, a plating liquid tends to soak into the boundary between the coating material and the molded article due to poor adhesivity of the material, which causes a decrease in the dimensional accuracy of the product. In addition, the same trouble would occur similarly as in the case of the resist when the coating material is removed.
Furthermore, electrical surface resistance of the base is reduced after the plating process or the circuit is formed, because the plating catalyst is added throughout the surface of the molded article.
Accordingly, it is an object of the present invention to provide a method for partially plating on a base made of a synthetic resin or other material which does not comprise resist application, hardening and removal processes so that no environmental problem due to organic solvents would occur while shortening the total process, electronic and electrical parts thus plated having outstanding dimensional accuracy, remarkable conductivity and high quality.
Using a water soluble polymer or hydrolyzable polymer as a coating material for coating a portion not to be plated, the above mentioned object can be achieved by;
[1] a method for partially plating on a base by the use of a plating catalyst comprising a coating process to coat a surface to be plated or not to be plated by means of a coating material selected from a water soluble polymer or hydrolyzable polymer either before or after a catalyst applying process to soak a container containing bases in a plating catalyst bath;
[2] in the above mentioned method, the base may include not only a single base but an assembly of a number of bases (the xe2x80x9cbasexe2x80x9d hereinafter means both a single unit and an assembly thereof, unless otherwise noted);
[3] the above mentioned method preferably comprises the following processes in order
(1) a roughing process to rough the base surface,
(2) a coating process to partially coat the roughed surface with a coating material selected from a water soluble polymer or hydrolyzable polymer,
(3) a catalyst applying process to apply a plating catalyst on the surface except an uncoated portion,
(4) a coated material removing process, and
(5) a plating process to plate on the catalyzed surface; or [4] the above mentioned method preferably comprises the following processes in order
(1) a coating process to partially coat a roughed surface with a coating material selected from a water soluble polymer or hydrolyzable polymer,
(2) a roughing process to rough the base surface except a coated area,
(3) a catalyst applying process to apply a plating catalyst on the roughed surface,
(4) a coated material removing process, and
(5) a plating process to plate on the catalyst applied surface; or [5] the above mentioned method preferably comprises the following processes in order
(1) a roughing process to rough the base surface,
(2) a catalyst applying process to apply a plating catalyst on the surface,
(3) a coating process to partially coat the surface with a coating material selected from a water soluble polymer or hydrolyzable polymer,
(4) a plating process to plate on the surface except an uncoated portion, and
(5) a coated material removing process, or [6] the above mentioned method preferably comprising the following processes in order
(1) a roughing process to rough the base surface,
(2) a catalyst applying process to apply a plating catalyst on the surface,
(3) a plating process,
(4) a coating process to partially coat the surface with a coating material selected from a water soluble polymer or hydrolyzable polymer,
(5) a removing process to remove a plated layer except the coated portion, and
(6) a coated material removing process.
In the cases of the methods and, the catalyst applying process (3) and the coated material removing process (4) may be conducted at the same time. Further, the catalyst applying process (3) may be followed by a preliminary plating process.
On the other hand, in the case of the method, an additional plating process may be conducted after the coated material removing process (5).